If you plan to use the Microsoft
SQL Server 2008 R2 Express database that is bundled with vCenter Server,
Microsoft Windows Installer version 4.5 (MSI 4.5) is required on your system.
You can download MSI 4.5 from the Microsoft Web site. You can also install MSI
4.5 directly from the vCenter Server
autorun.exe
installer.

The VMware vCenter Server Appliance can be
deploye d only on hosts that are running ESX version 4.x or ESXi version 4.x or
later.